Test circuit for use in a semiconductor apparatus

ABSTRACT

A test circuit that senses a misaligned probe during a test includes a first power control section that senses voltage levels of a plurality of sensing lines and controls power supplied to a lower circuit section provided below a part of a pad group, and a second power control section that selectively provides an internal voltage in response to a sensing result of the first power control section.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. 119(a) to Koreanapplication number 10-2007-0114122, filed on Nov. 9 2007, in the KoreanIntellectual Property Office, which is incorporated by reference in itsentirety as if set forth in full.

BACKGROUND

1. Technical Field

The embodiments described herein relate to a semiconductor apparatus,and more particularly, to a test circuit that can control power suppliedto a lower circuit section provided below a pad and monitor the resultthereof even when a test probe is not optimally placed on the pad.

2. Related Art

A conventional process for manufacturing a semiconductor chip includes afabrication process (FABrication Process; ‘FAB’process) that repeatedlyforms a specific circuit pattern in order to form an integrated circuiton a semiconductor substrate (wafer), and a test process that tests thecharacteristics of a semiconductor chip formed on the semiconductorsubstrate. After that, an assembly process for cutting the semiconductorsubstrate unit chips and packaging the chips is performed.

In the above-mentioned test process, specifically, a tip (or needle) ofa probe card of a tester comes in contact with a pad of thesemiconductor chip, and a signal is transmitted to the pad, so that itis possible to determine whether the semiconductor chip has defects ornot. However, as the number of pads to be probed increases, it isdifficult to accurately position a probe tip for signal transmission ateach of the pads. For this reason, the probe tip may not come in contactwith a normal portion of the pad, but rather may come in contact withonly an edge portion of the pad.

In a conventional chip, a characteristic monitoring circuit section,which can monitor parameter data such as characteristics of voltage andcurrent of an individual device used to operate the semiconductor chip,or an ESD (Electro-Static Discharge) circuit section may be providedbelow a part of the edge of the pad. If the probe tip is only contactingan edge of the pad, then, e.g., when excessive pressure is applied tothe probe tip, the circuit section provided below the pad may beshort-circuited to the pad. This can actually cause defects in the chipand/or can result in false test readings. As a result, the yield of thesemiconductor chip may be decreased.

SUMMARY

A test circuit for use in a semiconductor apparatus that can beconfigured to control power supplied to a lower circuit section providedbelow a pad and to monitor the result thereof even when a test probe isnot placed optimally on the pad.

According to one aspect, a test circuit for use in a semiconductorapparatus includes a first power control section that senses voltagelevels of a plurality of sensing lines and controls power supplied to alower circuit section provided below a part of a pad group, and a secondpower control section coupled with the first power control section, thesecond power control section configured to selectively provides aninternal voltage in response to a sensing result of the first powercontrol section.

The first power control section can include a sensing unit that sensesthe voltage levels of the plurality of sensing lines and provides apower enable signal, and a power supply unit that provides power to thelower circuit section in response to the power enable signal.

According to another aspect, a test circuit includes a sensing unit thatdetects voltage levels from a plurality of sensing lines provided belowthe edge portion of a first pad group, senses a short-circuit betweenthe first pad group and the sensing lines, and provides a power enablesignal, a power supply unit coupled with the sensing unit, the powersupply unit configured to control power supplied to a lower circuitsection provided below the first pad group in response to the powerenable signal, and a second power control section coupled with thesensing unit, the second power control section configured to selectivelyprovides a path for a signal transmitted to the second pad group inresponse to the power enable signal.

According to still another aspect, a semiconductor apparatus includesfirst and second pad groups that include an edge region surrounding aregion to be probed, and a test circuit that senses a short circuitbetween the first pad group and a plurality of sensing lines by usingthe plurality of sensing lines provided below a part of the edge regionof the first pad group, controls the operation of a specific circuitsection, and monitors the specific circuit section.

These and other features, aspects, and embodiments are described belowin the section entitled “Detailed Description.”

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thesubject matter of the present disclosure will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a top view of a semiconductor apparatus showing the layout ofpads and probe tips that probe the pads.

FIG. 1B is a cross-sectional view taken along a line B-B′ of FIG. 1A.

FIG. 2 is a conceptual diagram of a first pad group according to oneembodiment.

FIG. 3 is a block diagram of a test circuit according to one embodiment.

FIG. 4 is a circuit diagram of a sensing unit that can be included inthe test circuit shown in FIG. 3.

FIG. 5 is a circuit diagram of a power supply unit that can be includedin the test circuit shown in FIG. 3.

FIG. 6 is a circuit diagram of a second power control section that canbe included in the test circuit shown in FIG. 3.

FIG. 7 is a graph showing an output signal of the second power controlsection shown in FIG. 6.

DETAILED DESCRIPTION

When a test circuit according to the embodiments described herein isprovided, it is possible to sense whether there is an abnormalityrelated to a probe and/or its placement, to shut off power so that aspecific circuit section does not operate, and to monitor the specificcircuit section in order to rearrange the probes. That is, by providingsensing lines below a pad group the voltage levels of the sensing linescan be detected, and it is possible to sense whether the sensing linesare short-circuited to the pad, which can indicted an abnormalityrelated to the probe. Further, power can be shut off so that a specificcircuit section provided below the pad does not operate when anabnormality is detected, thereby preventing damage. Therefore, it ispossible to decrease the occurrence of defects.

FIGS. 1A and 1B are diagrams showing the relationship between probe tips10 and pads 20 of a semiconductor apparatus. FIG. 1A is a top viewshowing the layout of the probe tips 10 and the pads 20, and FIG. 1B isa cross-sectional view taken along a line B-B′ of FIG. 1A.

Referring to FIGS. 1A and 1B, there are provided a plurality of pads 20a and 20 b, a plurality of first probe tips 10 a disposed on side of thepads 20 at regular intervals, and a plurality of second probe tips 10 bdisposed on the other side of the pads 20 at regular intervals.

In detail, the first probe tips 10 a are connected to even-numberedrows, i.e., second pad group 20 b of the pads 20, and the second probetips 10 b are connected to odd-numbered rows, i.e., a first pad group 20a of the pads 20.Probe tips 10 a and 10 b disposed adjacent to eachother have different lengths to ensure the do not contact each other andto provide an area margin. For example, the first probe tips 10 adisposed at the even-numbered rows are composed of short probe tips andlong probe tips one after the other as are the second probe tips 10 bdisposed at the odd-numbered rows.

The ends of the probe tips 10 come in contact with the pads 20 so as totransmit electrical signals.

The physical region of the pad 20 can include a predetermined region (a)where the probe tip 10 comes in contact with the pad and an edge region(b) that surrounds the region. In the example of FIGS. 1A and 1B, thepredetermined region (a) is exemplified as a normal region that isprobed, but is not physically shown or defined. For the first pad group20 a, a separate lower circuit section (c) can be positioned below theedge region (b) of the pad. The second pad group 20 b can, e.g., be apower pad group where a separate circuit section is not provided belowthe edge region (b) of the pad unlike the first pad group 20 a. In thiscase, the lower circuit section (c) can be an ESD (Electro-StaticDischarge) circuit section or a circuit section for monitoringcharacteristics of a device, but is not limited thereto.

FIG. 2 is a top view of one of plurality of pads comprising the firstpad group 20 a according to one embodiment. Referring to FIG. 2, thelower circuit section (c) is provided below a portion of the edge region(b) of the first pad group 20 a. First to fourth sensing lines sen<0:3>,which can be configured to sense probe defects, are provided between thelower circuit section (c) and the first pad group 20 a.

An example configuration of the edge region (b), the sensing linessen<0:3>, and the lower circuit section (c) will be roughly describedbelow with reference to the cross-sectional view of FIG. 2.

In more detail, the lower circuit section (c) can be formed of a firstmetal layer metal 0, and the edge region (b) of the pad can be formed ofa pad metal layer, that is, a third metal layer metal 2. For example,the first metal layer can be an under metal layer, and the third metallayer can be a top metal layer. Therefore, the first to fourth sensinglines sen<0:3> can be formed of a second metal layer metal 1 that isdifferent from a pad metal layer and a metal layer of the lower circuitsection. Further, in order to prevent the metal layers from beingelectrically connected to one another, a first interlayer insulatingfilm 30 can be interposed between the lower circuit section (c) and thefirst to fourth sensing lines sen<0:3>, and a second interlayerinsulating film 40 can be interposed between the edge region (b) of thepad and the first to fourth sensing lines sen<0:3>. Accordingly, whenthe position of a probe tip (see 10 of FIG. 1A) deviates from a normalposition (a) and the probe tip comes in contact with the edge region (b)with excessive pressure, the first to fourth sensing lines sen<0:3> canbe short-circuited to the edge region (b). Therefore, it is possible tosense whether the position of the probe is off and/or if the position ofthe probe has the potential to cause a defect, by detecting voltagelevels of the first to fourth sensing lines sen<0:3>.

While four sensing lines are exemplified for convenience of description,it will be understood that the number of sensing lines can be increasedor decreased as required by a particular implementation. In other words,the embodiments described herein can use more or less sensing lines aslong as it s possible to sense whether the position of the probe is offand/or whether the lower circuit section (c) is short-circuited or not.

FIG. 3 is a block diagram of a test circuit 101 according to oneembodiment. Referring to FIG. 3, the test circuit 101 includes a powercontrol block 100 that can be configured to control power supplied topads 20 a and 20 b.

The power control block 100 can include a first power control section350 and a second power control section 400.

The first power control section 350 can include a sensing unit 200 and apower supply unit 300 the sensing unit 200 can be configured to sensevoltage levels from the first to fourth sensing lines sen<0:3> that areprovided below the first pad group 20 a, and supply a power enablesignal ‘ENPWR’.

The power supply unit 300 can be configured to provide power ‘PWR’to thelower circuit section (c) of the first pad group 20 a in response to thepower enable signal ‘ENPWR’.

In more detail, the sensing unit 200 can be configured to sense whetherthe edge region (see (b) of FIG. 2) of the pad and the first to fourthsensing lines sen<0:3> cause a short circuit. If the edge region (b) andthe first to fourth sensing lines cause a short circuit, then thesensing unit can deactivated the power enable signal ‘ENPWR’.Accordingly, the power supply unit 300 can control whether the power‘PWR’ is supplied to the lower circuit section (c) via the power enablesignal ‘ENPWR’. That is, when it is determined as a result of the testthat the probe is not positioned correctly, then power supply unit 300can prevent the power ‘PWR’ from being supplied to the lower circuitsection (c to decrease the occurrence of defects caused by shortingbetween the lower circuit section (c) and the probe.

The second power control section 400 can be configured to provideinternal voltages Vint, which are signals used for monitoring and areprovided through different paths, to the second pad group 20 b inresponse to the power enable signal ‘ENPWR’.

As described above, if it is determined by sensing whether the edgeregion (b) of the pad is short-circuited to any of the first to fourthsensing lines sen<0:3>, then the first power control section 350 can beconfigured not to supply power to the lower circuit section (c). Thefirst power control section 350 can be connected to a feedback loop andthus self-controlled. The feedback loop can be configured to feedbackthe process result for the lower circuit section (c). That is, when theprobe is incorrectly positioned, power is not supplied to the lowercircuit section (c), and the control operation is completed. As aresult, it can be difficult to determine in real time with which pads aproblem exists.

The second power control section 400 can be configured to monitor theinternal voltages Vint that are provided to the second pad group 20 busing the power enable signal ‘ENPWR’, and thereby determine which padshave a problem. This will be described in detail below.

FIG. 4 is a detailed circuit diagram of the sensing unit 200 shown inFIG. 3. The sensing unit 200 can include a first detection unit 210, asecond detection unit 250, and a combination unit 290.

In this case, the first detection unit 210 and the second detection unit250 can have the same structure and operation principle, but havedifferent input signals. Therefore, for convenience of description, onlythe first detection unit 210 will be described in detail.

First, the first detection unit 210 can be configured to compare anddetect voltages of two adjacent sensing lines sen<0, 1>, and can includea first precharge unit 220, a second precharge unit 230, and a firstcomparison unit 240.

The first precharge unit 220 can include a first NMOS transistor N1. Thefirst NMOS transistor N1 can include a gate to which external power VDDis applied, a source that is connected to a ground voltage GND, and adrain that is connected to a first sensing line sen<0>. The first NMOStransistor N1 can be turned on by the power VDD that is applied to thegate, and can precharge the first sensing line sen<0> with a low levelvoltage. In this case, the first NMOS transistor N1 can be a weaktransistor, and may be a transistor of which the gate has a long lengthand a narrow width. Therefore, until the first sensing line sen<0> isshort-circuited, the first precharge unit 220 precharges the firstsensing line sen<0> with a weak low level voltage.

The second precharge unit 230 can include a first PMOS transistor P1.The first PMOS transistor P1 can include a gate to which the groundvoltage GND is applied, a source to which external power VDD is applied,and a drain that is connected to the second sensing line sen<1>. Thefirst PMOS transistor P1 can be turned on by the ground voltage GND thatis applied to the gate, and can precharge the second sensing line sen<1>with a high level voltage. Like the above-mentioned first NMOStransistor N1, the first PMOS transistor P1 can be a weak transistor,and can precharge the second sensing line sen<1> with a weak high levelvoltage.

That is, until the first and second sensing lines sen<0, 1> arephysically short-circuited due to external pressure, the first andsecond precharge units 220 and 230 can be configured to precharge thefirst and second sensing lines sen<0, 1> so that signal levels of thefirst and second sensing lines are different from each other.

The first comparison unit 240 can be configured to compare the outputresults of the first and second precharge units 220 and 230. The firstcomparison unit 240 can include a first anticoincidence circuit EXOR1.Therefore, depending on an exclusive operation, if the output signals ofthe first and second precharge units 220 and 230 have a voltage levelhaving the same phase, then the comparison unit 240 can provide firstcomparison signal ‘com1’ at a low-level. Further, if the output signalsof the first and second precharge units 220 and 230 have voltage levelshaving different phases, then the comparison unit 240 can provide thefirst comparison signal ‘com1’ at a high-level.

The combination unit 290 can be configured to provide an activatedhigh-level power enable signal ‘ENPWR’ when both the first and secondcomparison signals com1 and com2, which are the output signals of thefirst and second detection units 210 and 250, are both at a high-level.

The detailed operation of the sensing unit 200 will now be describedwith reference to FIG. 4.

First, the operation will be described for the case where the sensinglines are short-circuited to the edge region (b) of the pad due to theincorrect positioning of the probe and excessive pressure placed on theprobe.

It should be noted that a diameter of an end-point of a probe tip (see10 of FIG. 1A) is on the order of several tens of micrometers, and adiameter of each of the first to fourth sensing lines sen<0:3> is in theorder of several micrometers. Therefore, when the probe tip (see 10 ofFIG. 1A) is short-circuited to the first to fourth sensing linessen<0:3> due to excessive pressure, then in fact at least two adjacentsensing lines will be short-circuited with each other and with the edgeregion (see 20 of FIG. 1A) of the pad. Therefore, the two adjacentsensing lines will have the same high-or low-level electric potential.

As an example, it can be assumed for the discussion that follows thatthe first and second sensing lines sen<0, 1> are short-circuited to theedge region (b), and have the same high-level electric potential.

The first and second sensing lines sen<0, 1> are precharged withdifferent voltage levels. However, once they are shorted, the first andsecond sensing lines have the same electric potential. Specifically,since each of the first and second precharge units 220 and 230 is a weaktransistor, the output signals of the first and second precharge units220 and 230 vary depending on the first and second sensing lines sen<0,1> to which signals are input. Therefore, since the same high-levelsignal is input to the comparison unit 240, the first comparison signal‘com1’ output from the first comparison unit 240 becomes a low-levelsignal.

Considering the combination of the results of the first and seconddetection units 210 and 250, when any one of the first and seconddetection units receives a low-level comparison signal, the combinationunit 290 provides a low-level power enable signal ‘ENPWR’.

That is, if the sensing lines are short-circuited to the edge region ofthe pad, then the sensing unit 200 provides a deactivated, low-levelpower enable signal ‘ENPWR’.

In contrast, when the sensing lines sen<0:3> are not short-circuited tothe edge region of the pad, then due to the first to fourth prechargeunits 220, 230, 260, and 270, the first to fourth sensing lines sen<0:3>correspond to a low level signal, a high level signal, a low levelsignal, and a high level signal, respectively, so that two adjacentsensing lines correspond to different level signals. Accordingly, firstand second high-level comparison signals ‘com1’and ‘com2’ are providedto the first and second detection units 210 and 250. Since thecombination unit 290 receives the first and second high-level comparisonsignals ‘com1’ and ‘com2’, the combination unit 290 can provide anactivated, high-level power enable signal ‘ENPWR’.

FIG. 5 is a circuit diagram of the first power supply unit 300 shown inFIG. 3. As can be seen, the power supply unit 300 can include a firstinverter IV1 and a third PMOS transistor P3.

The first inverter IV1 can receive and invert the power enable signal‘ENPWR’. The third PMOS transistor P3 can include a gate that receivesthe power enable signal ‘ENPWR’, a source to which power VDD is applied,and a drain that is connected to the power signal ‘PWR’. Accordingly,the third PMOS transistor P3 can be turned on in response to theinverted power enable signal ‘ENPWR’.

That is, when receiving a deactivated low-level power enable signal‘ENPWR’, the power supply unit 300 can be configured to shut off thepower signal ‘PWR’ supplied to the pad lower circuit section (c).However, when receiving an activated high-level power enable signal‘ENPWR’, the power supply unit 300 can be configured to supply the powersignal ‘PWR’ to the pad lower circuit section (c).

As described above, the first power control section 350 can beconfigured to sense that the pad is probed with excessive pressure, feedback an indication that such is the case, and supply power ‘PWR’ to thelower circuit section (c) provided below the pad or shuts off the power‘PWR’, so that it is possible to reduce the defects caused by excessivepressure On the probe when it is misaligned.

FIG. 6 is a detailed circuit diagram of the second power control section400. As can be seen, the second power control section 400 can beconfigured to monitor whether the probe is misaligned using the secondpad group 20 b. Specifically, the second power control section 400 canprovide a voltage, which is provided from an internal voltage generatingunit 500, as an internal voltage Vint in accordance with the signallevel of the input power enable signal ‘ENPWR’, or can provide thevoltage VDD, which is provided from the outside, as an internal voltageVint. As described above, the second pad group 20 b is exemplified as apower pad group.

Referring to FIG. 6, the second power control section 400 can include avoltage selection unit 410. The voltage selection unit 410 can includefirst and second switching units 412 and 414.

When being turned on in response to a power enable signal ‘ENPWR’ thatis inverted by a second inverter IV2, the first switching unit 412 canprovide the output voltage of the internal voltage generating unit 500as an internal voltage Vint.

The first switching unit 412 can include a fourth PMOS transistor P4.The fourth PMOS transistor P4 can include a gate that receives theinverted power enable signal ‘ENPWR’, a source that is connected to theinternal voltage generating unit 500, and a drain that is connected tothe second pad group 20 b.

When turned on in response to the power enable signal ‘ENPWR’, thesecond switching unit 414 can provide power VDD, which is supplied fromthe outside, as an internal voltage Vint. The second switching unit 414can include a fifth PMOS transistor P5. The fifth PMOS transistor P5 caninclude a gate that receives the power enable signal ‘ENPWR’, a sourceto which the voltage VDD is applied, and a drain that is connected tothe second pad group 20 b.

The operation of the second power control section 400 will now bedescribed.

When receiving the activated power enable signal ‘ENPWR’, the firstswitching unit 412 can be turned on and can provide the voltage, whichis output from the internal voltage generating unit 500, as the internalvoltage Vint. In this case, if monitoring the voltage from the secondpad group 20 b, a stable voltage level supplied from the internalvoltage generating unit 500 is monitored regardless of the power VDD.

However, when receiving the deactivated power enable signal ‘ENPWR’, thesecond switching unit 414 can be turned on and directly provide thepower VDD, as the internal voltage Vint. In this case, if monitoring thevoltage from the second pad group 20 b, it is possible to monitor avoltage level that is increased along the power VDD.

That is, the second power control section 400 can selectively provide asupply path of the internal voltage Vint in accordance with the signallevel of the power enable signal ‘ENPWR’, and can sense whether aproblem with the probe exists by measuring the voltage level through thesecond pad group 20 b. Therefore, when the probe is misaligned and theprobe comes in contact with the pad with excessive pressure, it ispossible to stop the test and realign the probe tips (see 10 of FIG. 1A)by using the monitoring result.

FIG. 7 is a graph showing a measurement result of the voltage level atthe second pad group 20b shown in FIG. 6.

Referring to FIG. 7, as described above, (i) when the power enablesignal ‘ENPWR’is an activated high-level signal, it can be seen that astable voltage level where the voltage level measured from the secondpad group 20 b is maintained constant regardless of the power VDD thatis supplied by the internal voltage generating unit (see 500 of FIG. 6)is measured. However, (ii) when the power enable signal ‘ENPWR’ is adeactivated low-level signal, it can be seen that the voltage levelmeasured from the second pad group 20 b does not have a stable range andan internal voltage Vint proportional to the voltage VDD is measured.

Thus, by using a test circuit configured according to the embodimentsdescribed herein, it is possible to sense whether probe misalignmentoccurs, to shut off power so that a specific circuit section does notoperate when misalignment occurs, and to monitor the specific circuitsection in order to rearrange the probes.

It will be apparent to those skilled in the art that variousmodifications and changes may be made without departing from the scopeand spirit of the embodiments described herein. Therefore, it should beunderstood that the above embodiments are not limitative, butillustrative in all aspects. The scope of the above embodiments aredefined by the appended claims rather than by the description precedingthem, and therefore all changes and modifications that fall within metesand bounds of the claims, or equivalents of such metes and bounds aretherefore intended to be embraced by the claims.

1. A test circuit comprising: a first power control section configuredto sense voltage levels of a plurality of sensing lines and to controlpower supplied to a lower circuit section provided below a part of a padgroup; and a second power control section coupled with the first powercontrol section, the second power control section configured toselectively provide an internal voltage in response to a sensing resultof the first power control section.
 2. The test circuit of claim 1,wherein the first power control section comprises: a sensing unitconfigured to determine whether the plurality of sensing lines isshort-circuited by detecting and comparing the voltage levels of theplurality of sensing lines, and to provide a power enable signal; and apower supply unit coupled with the sensing unit, the power supply unitconfigured to provide power to the lower circuit section in response tothe power enable signal.
 3. The test circuit of claim 2, wherein thesensing unit comprises: a plurality of detection units each configuredto detect and compare signal levels of two adjacent sensing lines and tooutput a signal based thereon; and a combination unit coupled with theplurality of detection units, the combination unit configured to providean activated power enable signal when all of the signals output from theplurality of detection units are activated.
 4. The test circuit of claim3, wherein each of the plurality of the detection units comprise: firstand second precharge units configured to precharge the adjacent sensinglines with different voltage levels; and a comparison unit configured tocompare signal levels of the adjacent sensing lines.
 5. The test circuitof claim 4, wherein the first and second precharge units are configuredto precharge the adjacent sensing lines with a ground voltage and avoltage that is supplied from the outside, respectively.
 6. The testcircuit of claim 4, wherein if the signal levels of the sensing linesare equal to each other, then the comparison unit is configured toprovide a low-level comparison signal.
 7. The test circuit of claim 2,wherein the power supply unit provides a voltage, which is supplied fromthe outside, in response to the power enable signal.
 8. The test circuitof claim 1, wherein further comprising an internal voltage generatingcircuit; and wherein the first power control section is furtherconfigured to generate a power enable signal based on the voltage levelsof a plurality of sensing lines, and wherein the second power controlsection comprises: a first switching unit configured to provide avoltage signal generated by the internal voltage generating circuit asthe internal voltage when the power enable signal is activated; and asecond switching unit configured to provide external power as theinternal voltage when the power enable signal is deactivated.